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A small wooden boat found off the western island of Sado in Japan contained decomposing bodies, according to local police.

The boat was badly damaged and contained faint markings on the side that appeared to be Korean characters, according to the Sado West Police. But the characters were so faint that they could not read it clearly, said Toshiyuki Kojima, deputy chief of Sado Nishi Police Station.

The boat was discovered early morning Wednesday, drifting into a rocky part of the coast at Mano Bay in Sado City. Authorities did not know how long the boat had been there.

Police would not say exactly how many bodies were found on the boat, but said that some bodies had decomposed to the point where only skeletons remained.